Headteachers blame teenagers' love of chips and dislike of healthy food for a slump in the take-up of school meals in nearly a third of all secondary schools in England, according to a survey today.

A similar proportion reported an increase, however, with no change in about 40% of secondaries. While the picture is much better in primary schools - where over 80% report that take-up has either increased or remained the same - the survey findings underline the challenge facing schools as a result of higher nutritional standards introduced as a result of celebrity chef Jamie Oliver's crusade to improve the standards of meals.

The survey was carried out by the School Food Trust - appointed by the government to oversee the new drive to improve school food - and is the first poll of headteachers since schools and local authorities were required to introduce new nutritional standards last September. As a result of the changes, traditional favourites such as burger and chips have been replaced with more fresh fruit, vegetables and fish.

Headteachers belonging to the trust's panel completed a detailed questionnaire in February. The data will be be published on the SFT's website today. It reveals that take-up of school meals in the autumn term last year compared with the same time in 2005 fell in 29.7% of secondary schools and 18% of primary schools. Take-up increased in 29.7% of secondary schools and 33% of primary schools, while it was unchanged in 49% of all primaries and 40.5% of secondaries.

Of those reporting a decrease in take-up, over two thirds blamed a dislike of healthier options or new menus.

Price increases - meals are typically up to £1.80 from £1.50 before the changes - were also a factor.

The findings come amid evidence of healthier eating among families in general.

Government figures published yesterday revealed that fruit and vegetable purchases excluding potatoes for the average household were 7.7% higher in 2005-06, the largest rise in the last 20 years.

Fruit purchases were up by more than 10%, while confectionery purchases fell by 6.1%.